The present invention relates to a method and apparatus for relining an underground gas line or the like without requiring excavation. More particularly, the present invention relates to a method and apparatus in which a flexible tubing may be passed through an existing underground line with the ends thereof sealed to the interior of the pipeline at a point beyond the defect by means of a heat responsive expandable sealing unit.
The present invention is applicable to the repair of any inaccessible line. Very often, the line is inaccessible because it is an underground line. However, the present invention has been made particularly with respect to the repair of underground gas lines without the need of excavation, and more particularly, the repair of gas service lines or lines leading from the gas main to individual buildings, such as homes. Gas lines of this type are often installed and remain in existence for many years, very often for periods of time greatly in excess of twenty years. Very often, after a period of twenty or more years, such service lines may tend to deteriorate, especially due to the fact that they are underground and are not in an ideal environment. The repair of such service lines is normally an expensive operation. It is necessary to excavate to a gas service line, usually for the entire length of the building to the point where the gas line connects to the main. This usually requires excavation to or into the street, and usually through the sidewalk. There is usually substantial expense in this excavation and the necessary refilling and repaving operations.
Attempts in the past to repair underground lines have been made to mechanically install a rigid pipe within the existing pipeline in order to avoid excavation. However, the mechanical attachment has not been satisfactory, particularly as applied to gas lines. Furthermore, insertion of a metal pipe inside of an existing pipe required that the existing pipeline be perfectly straight. Examples of this type of prior art technology may be seen in U.S. Pat. Nos. 2,731,041; 2,756,779; 2,784,627 and 2,926,701. Attempts have also been made to seal leaking underground lines by forcing a sealing fluid under pressure into the line, with the sealing fluid infiltrating through the fault in the line and sealing the fault from further infiltration. This is shown by U.S. Pat. No. 3,710,812. Further, an attempt has been made to coat the interior of an underground line by a coating process to coat the interior of the pipeline after cleaning operations as shown in U.S. Pat. No. 3,211,573. These prior art attempts have proved to be ineffective in many cases such as curved line and deteriorating pipe, cumbersome in the number of steps required and expensive.